Red Channel Noise Reduction Comparison

This 5 megapixel image was shot with a Nikon Coolpix 5000.
The red squares indicate the 100% crops below to show the effect of different methods to reduce "Red Channel Noise" or "Color Noise".
The "Original" crops are compared with my new noise removal method and three other automated Adobe Photoshop actions developed by other people (named "Other 1", "Other 2", and "Other 3").

parison
Sky Crop - RGB
Original
123di
Other 1
Other 2
Other 3

Above are 100% crops. Differences are more visible at 200% crops below or by looking at the red channel crops. A slight level adjustment has been applied to the 200% RGB crop to bring out the red waves in the blue sky.

How much noise you see depends also on the quality of your monitor, its dynamic range and how well it is calibrated. So looking in the "Red Channel Only" examples below might be easier.
Sky Crop - Red Channel Only - 100% and 200%
Original
123di
Other 1
Other 2
Other 3
Red Channel Histogram Standard Deviation
4.71
1.71
2.67
2.22
2.94

The red channel is very noisy as is reflected by a red channel histogram standard deviation of 4.71 in this blue sky crop. My method creates a clean blue sky with a standard deviation of only 1.71, which is about the same as what you would measure in the blue sky of a typical Canon EOS D60 picture, which is of course not the same as saying the image quality is now the same. The other methods reduce the standard deviation as well, but create a "wavy" pattern in the red channel which will be barely visible at 100% on a monitor but will often be clearly visible in silver-halide enlargements.

 
Edges Crop - RGB
Original
123di
Other 1
Other 2
Other 3

My method leaves clean crisp edges, actually even a bit cleaner than the original and this before applying any sharpening. Other 2 does a good job as well, but Other 1 and Other 3 blur the edges significantly.
Edges Crop - Red Channel Only
Original
123di
Other 1
Other 2
Other 3

The above mentioned differences are again more visible in the red channel.

 
Shadow Crop - RGB
Original
123di
Other 1
Other 2
Other 3

The noise is also reduced in the shadow areas by all methods. Differences between methods are less obvious than in the blue sky crops and again more visible in the red channel.
 
Shadow Crop - Red Channel Only
Original
123di
Other 1
Other 2
Other 3

My method creates again the smoothest shadows, followed by Other 2, but notice the fuzzy edges of the yellow rooftop in the Other 3 method.
 
So how does my method work ? That is featured in my new e-book: